Zusammenfassung der Ressource
Covalent
substances
- Simple molecular substances
- The atoms form very strong covalent bonds
to form small molecules of several atoms.
- By contrast, the forces of attraction
between these molecules are very weak.
- The result of these week intermolecular forces is that
the melting and boiling points are very low.
- This is because the molecules
are easily parted from each other.
- Most molecular substances are gasses or liquids
at room temperature, but they can be solids.
- Molecular substances don't conduct electricity
- there are no ions so no electrical charge.
- Giant covalent structure (macromolecules)
- These are similar to giant ionic structures
(lattices) except that there is no charged ions.
- All the atoms are bonded to each other by strong covalent bonds.
- They have very high melting and boiling points.
- They don't conduct electricity
(except from graphite)
- The main examples are
diamond and graphite, which are
only made from carbon atoms.
- Diamond
- Each carbon atom forms 4 covalent
bonds in a very rigid structure.
- This makes diamond very hard.
- Graphite
- Each carbon atom forms 3 covalent
bonds. This creates layers which are
free to slide over each other.
- This makes graphite soft and slippery.
- The layers are held together so loosely that
they can be rubbed off onto paper (pencil).
- Graphite is the only non-metal which is a
good conductor of heat and electricity.
- Each carbon atom has 1 delocalised (free) electron and its
these free electrons that conduct the electricity and heat.